The transformation of material by heating, especially in the absence of oxygen, is called pyrolysis. Pyrolyzed wood, for example, produces biochar, which is a useful material both for increasing soil fertility and also burying excess carbon. However, commercial methods have focused on fast pyrolysis, which produces more oil, often of sub-optimal quality, and requires expensive separate drying steps, and methods to separate the solids from the gaseous products. Other smaller scaler methods feature the burning of the hydrocarbon fumes from the pyrolysis in order to generate the required heat. This causes harmful emissions, and also wastes a valuable hydrocarbon product.
Disk mills have long been used to grind material to smaller sizes. Shear pyrolysis, also known as ablative pyrolysis, adds friction for generating heat. A shear reactor has been described by the Applicant in U.S. Pat. No. 9,011,646 “Mechanical Pyrolysis in a Shear Retort.” It can be applied to many types of feeds such as biowaste, garbage, coal, ore for solvent mining, coke, waste ash, oil sands and shale. Any mineral content or ash is an asset to the grinding friction, rather than a liability. Supplemental heating elements for such a reactor are part of the Applicant's U.S. Pat. No. 9,851,145 “Radial Counterflow Reactor with Applied Radiant Energy.”
However, this shear retort design does not detail how the management of the extrusion of the pyrolyzed material at the disk edges can be used to reuse the heat for pyrolysis, or how an indirect drive method for one of the disk surfaces can be moderated by a brake. The existing design also does not include the enclosure of the extruded material, to retain heat and fumes and prevent fires from the premature exposure of the hot material to oxygen. It also does not describe how a built-in shredder can improve the feed process by reducing the particle size prior to the final pyrolysis. This design also does not address the issues involved with the feed coming in from the top of the device, including how to keep the exhaust gas stream separated from the incoming feed stream.
What is needed is a design with enclosure of the extruded feed, a built-in shredder to improve feed particle size, a separated exhaust gas outlet, and an improved drive mechanism that can be driven by a single motor, and improved temperature control.